This invention relates to a camera capable of performing real zooming by varying the focal length of a taking lens, and pseudo zooming by varying pseudo print format.
There has been known a camera in which pseudo telephoto print information such as pseudo magnification is recorded on an exposed film or the like. The pseudo print information is used to produce a pseudo telephoto print by enlarging a part of an image on the nagative to a desired view field angle.
Japanese Unexamined Patent Publication No. 61-295534, for example, discloses a camera in which pseudo print information is written on a near portion of an exposed film frame when photography is executed in a pseudo zooming. During the printing process, a central portion of the negative frame which has been exposed in the pseudo zooming is enlarged in accordance with the written pseudo print information. Consequently, the same print can be obtained as photographed in the real zooming having the same magnification.
Also, Japanese Unexamined Patent Publication No. 62-135818 discloses a camera capable of performing real zooming and pseudo zooming in which pseudo print information is written on a portion of an exposed film frame which is not to be printed in the printing process.
Further, Japanese Unexamined Patent Publication No. 63-29821 discloses a camera carrying a program having a plurality of selectable control curves defined by object distances and pseudo magnifications. Only a pseudo magnification is calculated in accordance with a detected object distance and a selected control curve. This camera has only function of performing pseudo zooming. In other words, photography is executed at a fixed real focal length. In the printing process, a central portion of the nagative is enlarged at the calculated pseudo magnification to have a pseudo zoomed image.
Moreover, there has been known a camera having a zoomable taking lens in which it is carried out based on a detected object distance to calculate such a focal length as to provide a predetermined magnification, and the taking lens is automatically operated to attain the calculated focal length.
However, it will be seen that these conventional cameras have the following drawbacks.
The cameras of Japanese Unexamined Patent Publication Nos. 61-295534 and 62-135818 have the two functions of real zooming and pseudo zooming, However, these camera cannot automatically calculate a proper focal length in accordance with a detected object distance and then automatically adjust the taking lens to have the proper focal length. It is necessary to adjust the taking lens manually. Accordingly, in the case of photographing a moving object, it is very difficult to attain a proper view field angle soon.
On the other hand, the camera of Japanese Unexamined Patent Publication No. 63-29821 and the last-mentioned camera can automatically calculate a proper focal length in accordance with a detected object distance and then automatically adjust the taking lens to have the proper focal length. However, these camera cannot perform only one of real zooming and pseudo zooming. Accordingly, these cameras provide smaller magnification ranges than cameras having two functions of real zooming and pseudo zooming.
Also, in the camera of Japanese Unexamined Patent Publication No. 61-295534, a priority is given to the real zooming. When a desired magnification is beyond the magnification of the real zooming, the pseudo zooming is put in work. If the camera carries a certain taking lens whose f-number varies with a focal length variation, the shutter speed becomes slower when the object is dimmer, a photography error is likely to occur due to a camera shake. For example, when a taking lens having a focal length range of 35 mm to 70 mm and a f-number range of 4.0 to 5.6 is zoomed twofold, the exposure value lowers 1Ev. In this case, if a dark object is photographed in the real zooming, the shutter speed is considerably slowed and the photography receives a worse influence of camera shake. The real zooming photography becomes more difficult with the f-number range being greater.
Also, in flash photography, a flash light coverage distance which a flash light can reach is comparatively small. Accordingly, only near objects can be photographed in the real zooming by a flash light. Thus, zooming photography cannot fully be carried out. Specifically, when the guide number of a flash device is Gno, and the f-number of the taking lens is Fno, the flash light coverage distance d can be expressed as follows: EQU d=Gno / Fno
Accordingly, it will be seen that the f-number increases with the focal length of the taking lens being increased, the flash light coverage distance then decreasing. In other words, proper flash photography is limited in nearer objects.
Furthermore, in the above-mentioned cameras, changing of the view field angle inevitably requires driving of the taking lens. Consequently, a longer time is consumed to set the taking lens at a proper focal length. Particularly, in the camera in which the taking lens is automatically driven, the driving of the taking lens is executed each time an object moves. Accordingly, photography setting cannot be attained promptly. Also, the taking lens is driven by use of electrically driven motor. Accordingly, unnecessary electrical power is consumed to drive the taking lens.